/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.db.mpp.aggregation.slidingwindow;

import org.apache.iotdb.db.mpp.aggregation.Accumulator;
import org.apache.iotdb.db.mpp.plan.planner.plan.parameter.AggregationStep;
import org.apache.iotdb.db.mpp.plan.planner.plan.parameter.InputLocation;
import org.apache.iotdb.tsfile.read.common.block.column.Column;

import java.util.Comparator;
import java.util.List;

/**
 * When computing MAX_VALUE, MIN_VALUE, EXTREME, we only add partial aggregation results that
 * maintain monotonicity to queue. The aggregation result always appears at the head of the queue.
 */
public class MonotonicQueueSlidingWindowAggregator extends SlidingWindowAggregator {

    private final Comparator<Column> comparator;

    public MonotonicQueueSlidingWindowAggregator(
            Accumulator accumulator,
            List<InputLocation[]> inputLocationList,
            AggregationStep step,
            Comparator<Column> comparator) {
        super(accumulator, inputLocationList, step);
        this.comparator = comparator;
    }

    @Override
    protected void evictingExpiredValue() {
        while (!deque.isEmpty() && !curTimeRange.contains(deque.getFirst().getTime())) {
            deque.removeFirst();
        }
        this.accumulator.reset();
        if (!deque.isEmpty()) {
            this.accumulator.addIntermediate(deque.getFirst().getPartialResult());
        }
    }

    @Override
    public void processPartialResult(PartialAggregationResult partialResult) {
        if (partialResult.isNull()) {
            return;
        }

        while (!deque.isEmpty()
                && comparator.compare(
                partialResult.getPartialResult()[0], deque.getLast().getPartialResult()[0])
                > 0) {
            deque.removeLast();
        }
        deque.addLast(partialResult);
        this.accumulator.addIntermediate(deque.getFirst().getPartialResult());
    }
}
